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Error vacuo, Detecting Structures in Poorly Calcified Jurassic Dasycladales
Full text linkSeveral Jurassic dasycladalean genera (e.g. Pseudoclypeina, Palaeodasycladus, Eodasycladus, Chinianella and Cylindroporella) display a complex structure which, owing to a deficit of calcification, is difficult to interpret. This lack of calcification causes a loss of certain soft algal structures and complicates the work of the specialist responsible for interpreting the algal anatomy as well as the corresponding position in the systematics. A key of interpretation is given, and case histories are discussed
The genus Linoporella Steinmann, 1899 and its type-species Linoporella capriotica (Oppenheim, 1889) from the Early Cretaceous of Capri Bollettino della Società Paleontologica Italiana
No full textSystematical position of Acroporella assurbanipali Elliott with note on the genus Neomeris
No full textShallow carbonate platform bioevents during the Upper Triassic- Lower Jurassic: an evolutive interpretation
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Early Cretaceous dendritic shrub-like fabric in karstified peritidal carbonates from southern Italy
No full textLower Cretaceous (Valanginian) dendritic microfabrics occur in karstic cavities within fine-grained shallowmarine
platform carbonates at San Lorenzello, southern Italy. They form dense micritic masses and clusters,
generally oriented perpendicularly to cavity surfaces, surrounded by layered sparry cement. Individual dendrites,
typically sub-millimetric in size, have highly irregular margins and form distinctive shrub-like masses ranging
from compact and squat, to elongate and highly branched. The centimetric and irregularly elongate cavities
appear to have formed through subaerial exposure, and are almost entirely filled by the micritic dendrites and
associated sparry crusts. In size, shape and micritic composition, the dendrites broadly resemble a variety of
similar fabrics, including hot spring travertine shrubs and calcified microfossils such as Cambrian Angusticellularia,
which has analogs in present-day lacustrine calcified cyanobacteria. However, the San Lorenzello dendrites differ
in occupying small cavities. This cryptic microkarstic dripstone setting, together with the often regular spacing
and appearance of these dendritic fabrics, may be more consistent with an abiotic origin. These comparisons underscore
the challenge of interpreting microdendritic carbonates fabrics in general
New data on some type-species of Maastrichtian–Paleocene Dasycladales (green algae) from Iran Part III. Rostroporella Segonzac 1971
No full textRostroporella oviformis Segonzac represents the type species of the monospecific genus Rostroporella described from the Thanetian of France (type locality). Well preserved material of this large-sized dasycladale from the Paleocene of Iran (central and east Iran, and Zagros Zone, SW Iran), allows a better characterization of the algal thallus, e.g.,shape of the thallus, reproductive structures and the ranges of biometric parameters. The thallus is thought to be moniliform with ovoid articles. The reproduction with comparably large, elongated gametophores disposed laterally above the first order laterals refers to the goniosporate type. The suprageneric position of Rostroporella, previously placed within the family Polyphysaceae (formerly Acetabulariaceae), is discussed and transferred into the family Bornetellaceae
Upper Eocene coralline-orthophragminid facies from the Klokova Mountain (Southern Greece)
No full textFossil coralline
Evidence of external gametophores in puzzling Late Triassic-Early Jurassic dasycladalean green algae
Full text linkThe mineralized cover preserving soft parts of the Dasycladales, as an external mould, is the only tool allowing to deduce the anatomical parts of these algae. Problems arise when voids within the calcareous skeleton do not reflect accurately the original soft parts due to a loss of mineralization. Based on a rich material collected from the type locality in Languedoc (France), a detailed study was carried out on Chinianella ellenbergeri, the type species of Chinianella. Previous interpretation of voids in the calcified fossil considered the alga to be made of an alternation of fertile and further ramified sterile whorls. Our study shows that large cavities previously interpreted as corresponding to fertile whorls, actually denote empty spaces. Therefore, the alga essentially consists of spaced-out whorls of sterile primary laterals, distally bearing a tuft of three-four phloiophorous secondary laterals. A small number of specimens show the presence of calcified structures interpreted as corresponding to external, subterminal reproductive organs. Consequently, an emended diagnosis is proposed for C. ellenbergeri and for the Chinianella. Present interpretation of Chinianella adds a new step
to the understanding of the emergence of external reproductive organs during the geological history of this group of green algae. Chinianella ellenbergeri shows that choristosporate reproduction sensu lato was already well represented and diversified in the Early Jurassic. Other Late Triassic-earliest Jurassic species formerly attributed to Chinianella (namely C. carpatica, C. crosii, C. zanklii, C. micropora, and C. macropora) reveal that the large, fertile primary lateral is a compound pore with a structure like in Cymopolia, i.e., made of a short primary lateral with a terminal gametophore embraced by secondary laterals. Therefore, these species have been referred to the new genus Distefanopolia
New dasycladalean algae from the Norian (Upper Triassic) of Northern Italy (Mt. Pramaggiore, Carnian Prealps)
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